This invention relates to a structure of a cylindrical lock. According to the U.S. patent application Ser. No. 07/340,753, entitled "Lock Set with Spindle Lock", it relates to the structure of a tubular lock. Both the inside and outside knobs are locked simultaneously and not turnable after the lock is locked. Therefore, the inside and outside knobs cannot be turned to unlock the lock after the lock is locked. To open the door, the turning button of the inside knob has to turn back or a suitable key must be inserted to turn the turning button of the outside knob. Then the inside knob and the outside knob will be turnable. A trumpet lock, which can be unlocked by turning the inside knob from the inside of a door, is better than a tubular lock. Hence it will be pitiful for time delay or the ignorance of the child in some emergency situations.